R=120;
C=33e-12;
T=1e-8;
F=10e6;
t=0:T:1e-6;
S=10*cos(2*pi*F*t);

for k=2:length(t)
U(1)=0;
U(k)=(S(k)+(tau/T)*U(k-1))/(tau/T+1);
end;

plot(t,U);

